Molecular and non-molecular structure of substances. Structure of matter
It is not individual atoms or molecules that enter into chemical interactions, but substances. Substances are classified according to the type of bond molecular And non-molecular structure. Substances made up of molecules are called molecular substances. The bonds between molecules in such substances are very weak, much weaker than between atoms inside the molecule, and even at relatively low temperatures they break - the substance turns into a liquid and then into a gas (sublimation of iodine). The melting and boiling points of substances consisting of molecules increase with increasing molecular weight. TO molecular substances include substances with an atomic structure (C, Si, Li, Na, K, Cu, Fe, W), among them there are metals and non-metals. To substances non-molecular structure include ionic compounds. Most compounds of metals with non-metals have this structure: all salts (NaCl, K 2 SO 4), some hydrides (LiH) and oxides (CaO, MgO, FeO), bases (NaOH, KOH). Ionic (non-molecular) substances have high melting and boiling points.
Solids: amorphous and crystalline
Solids are divided into crystalline and amorphous.
Amorphous substances they do not have a clear melting point - when heated, they gradually soften and turn into a fluid state. For example, plasticine and various resins are in an amorphous state.
Crystalline substances characterized by the correct arrangement of the particles of which they consist: atoms, molecules and ions - at strictly defined points in space. When these points are connected by straight lines, a spatial framework is formed, called a crystal lattice. The points at which crystal particles are located are called lattice nodes. Depending on the type of particles located at the nodes of the crystal lattice and the nature of the connection between them, four types of crystal lattices are distinguished: ionic, atomic, molecular and metallic.
Crystal lattices are called ionic, at the nodes of which there are ions. They are formed by substances with ionic bonds, which can bind both simple ions Na+, Cl -, and complex SO 4 2-, OH -. Consequently, salts and some oxides and hydroxides of metals have ionic crystal lattices. For example, a sodium chloride crystal is built from alternating positive Na + and negative Cl - ions, forming a cube-shaped lattice. The bonds between ions in such a crystal are very stable. Therefore, substances with an ionic lattice are characterized by relatively high hardness and strength, they are refractory and non-volatile.
Crystalline lattice - a) and amorphous lattice - b).
Crystalline lattice - a) and amorphous lattice - b). Atomic crystal lattices
Atomic are called crystal lattices, in the nodes of which there are individual atoms. In such lattices the atoms are connected to each other very strong covalent bonds. An example of substances with this type of crystal lattices is diamond, one of the allotropic modifications of carbon. Most substances with an atomic crystal lattice have very high melting points (for example, for diamond it is over 3500 ° C), they are strong and hard, and practically insoluble.
Molecular crystal lattices
Molecular called crystal lattices, in the nodes of which molecules are located. Chemical bonds in these molecules can be both polar (HCl, H 2 O) and non-polar (N 2, O 2). Despite the fact that the atoms inside the molecules are connected by very strong covalent bonds, weak forces of intermolecular attraction act between the molecules themselves. Therefore, substances with molecular crystal lattices have low hardness, low melting points, and are volatile. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).
Molecular crystal lattice(carbon dioxide) Metal crystal lattices
Substances with metal bond have metal crystal lattices. At the nodes of such lattices there are atoms and ions(either atoms or ions into which metal atoms easily transform, giving up their outer electrons “for common use”). This internal structure of metals determines their characteristic physical properties: malleability, plasticity, electrical and thermal conductivity, characteristic metallic luster.
Cheat sheets
Atomic-molecular science was developed and first applied in chemistry by the great Russian scientist M.V. Lomonosov. The main provisions of this doctrine are set out in the work “Elements of Mathematical Chemistry” (1741) and a number of others. The essence of Lomonosov's teachings can be reduced to the following provisions.
1. All substances consist of “corpuscles” (as Lomonosov called molecules).
2. Molecules consist of “elements” (as Lomonosov called atoms).
3. Particles - molecules and atoms - are in continuous motion. The thermal state of bodies is the result of the movement of their particles.
4. Molecules of simple substances consist of identical atoms, molecules of complex substances - of different atoms.
67 years after Lomonosov, the English scientist John Dalton applied atomistic teaching to chemistry. He outlined the basic principles of atomism in the book “A New System of Chemical Philosophy” (1808). At its core, Dalton's teaching repeats Lomonosov's teaching. However, Dalton denied the existence of molecules in simple substances, which is a step backward in comparison with Lomonosov’s teaching. According to Dalton, simple substances consist only of atoms, and only complex substances consist of “complex atoms” (in the modern sense, molecules). The atomic-molecular theory in chemistry was finally established only in the middle of the 19th century. At the international congress of chemists in Karlsruhe in 1860, definitions of the concepts of molecule and atom were adopted.
A molecule is the smallest particle of a given substance that has its chemical properties. The chemical properties of a molecule are determined by its composition and chemical structure.
An atom is the smallest particle of a chemical element that is part of the molecules of simple and complex substances. The chemical properties of an element are determined by the structure of its atom. This leads to a definition of an atom that corresponds to modern concepts:
An atom is an electrically neutral particle consisting of a positively charged atomic nucleus and negatively charged electrons.
According to modern concepts, substances in gaseous and vaporous states are made up of molecules. In the solid state, only substances whose crystal lattice has a molecular structure consist of molecules. Most solid inorganic substances do not have a molecular structure: their lattice does not consist of molecules, but of other particles (ions, atoms); they exist in the form of macrobodies (crystal of sodium chloride, piece of copper, etc.). Salts, metal oxides, diamond, silicon, and metals do not have a molecular structure.
Chemical elements
Atomic-molecular science made it possible to explain the basic concepts and laws of chemistry. From the point of view of atomic-molecular theory, a chemical element is each individual type of atom. The most important characteristic of an atom is the positive charge of its nucleus, which is numerically equal to the atomic number of the element. The value of the nuclear charge serves as a distinctive feature for different types of atoms, which allows us to give a more complete definition of the concept of an element:
Chemical element- This is a certain type of atom with the same positive charge on the nucleus.
There are 107 known elements. Currently, work continues on the artificial production of chemical elements with higher atomic numbers.
All elements are usually divided into metals and non-metals. However, this division is conditional. An important characteristic of elements is their abundance in the earth’s crust, i.e. in the upper solid shell of the Earth, the thickness of which is assumed to be approximately 16 km. The distribution of elements in the earth's crust is studied by geochemistry - the science of the chemistry of the Earth. Geochemist A.P. Vinogradov compiled a table of the average chemical composition of the earth's crust. According to these data, the most common element is oxygen - 47.2% of the mass of the earth's crust, followed by silicon - 27.6, aluminum - 8.80, iron -5.10, calcium - 3.6, sodium - 2.64, potassium - 2.6, magnesium - 2.10, hydrogen - 0.15%.
Covalent chemical bond, its varieties and mechanisms of formation. Characteristics of covalent bonds (polarity and bond energy). Ionic bond. Metal connection. Hydrogen bond
The doctrine of chemical bonding forms the basis of all theoretical chemistry.
A chemical bond is understood as the interaction of atoms that binds them into molecules, ions, radicals, and crystals.
There are four types of chemical bonds: ionic, covalent, metallic and hydrogen.
The division of chemical bonds into types is conditional, since they are all characterized by a certain unity.
An ionic bond can be considered as an extreme case of a polar covalent bond.
A metallic bond combines the covalent interaction of atoms using shared electrons and the electrostatic attraction between these electrons and metal ions.
Substances often lack limiting cases of chemical bonding (or pure chemical bonding).
For example, lithium fluoride $LiF$ is classified as an ionic compound. In fact, the bond in it is $80%$ ionic and $20%$ covalent. It is therefore more correct, obviously, to talk about the degree of polarity (ionicity) of a chemical bond.
In the series of hydrogen halides $HF—HCl—HBr—HI—HAt$ the degree of bond polarity decreases, because the difference in the electronegativity values of the halogen and hydrogen atoms decreases, and in astatine hydrogen the bond becomes almost nonpolar $(EO(H) = 2.1; EO(At) = 2.2)$.
Different types of bonds can be found in the same substances, for example:
- in bases: between the oxygen and hydrogen atoms in hydroxo groups the bond is polar covalent, and between the metal and the hydroxo group it is ionic;
- in salts of oxygen-containing acids: between the non-metal atom and the oxygen of the acidic residue - covalent polar, and between the metal and the acidic residue - ionic;
- in ammonium, methylammonium salts, etc.: between nitrogen and hydrogen atoms - covalent polar, and between ammonium or methylammonium ions and the acid residue - ionic;
- in metal peroxides (for example, $Na_2O_2$), the bond between oxygen atoms is covalent nonpolar, and between the metal and oxygen is ionic, etc.
Different types of connections can transform into one another:
— during electrolytic dissociation of covalent compounds in water, the covalent polar bond turns into an ionic bond;
- when metals evaporate, the metal bond turns into a nonpolar covalent bond, etc.
The reason for the unity of all types and types of chemical bonds is their identical chemical nature - electron-nuclear interaction. The formation of a chemical bond in any case is the result of electron-nuclear interaction of atoms, accompanied by the release of energy.
Methods for forming covalent bonds. Characteristics of a covalent bond: bond length and energy
A covalent chemical bond is a bond formed between atoms through the formation of shared electron pairs.
The mechanism of formation of such a bond can be exchange or donor-acceptor.
I. Exchange mechanism operates when atoms form shared electron pairs by combining unpaired electrons.
1) $H_2$ - hydrogen:
The bond arises due to the formation of a common electron pair by $s$-electrons of hydrogen atoms (overlapping $s$-orbitals):
2) $HCl$ - hydrogen chloride:
The bond arises due to the formation of a common electron pair of $s-$ and $p-$electrons (overlapping $s-p-$orbitals):
3) $Cl_2$: in a chlorine molecule, a covalent bond is formed due to unpaired $p-$electrons (overlapping $p-p-$orbitals):
4) $N_2$: in a nitrogen molecule three common electron pairs are formed between the atoms:
II. Donor-acceptor mechanism Let us consider the formation of a covalent bond using the example of the ammonium ion $NH_4^+$.
The donor has an electron pair, the acceptor has an empty orbital that this pair can occupy. In the ammonium ion, all four bonds with hydrogen atoms are covalent: three were formed due to the creation of common electron pairs by the nitrogen atom and hydrogen atoms according to the exchange mechanism, one - through the donor-acceptor mechanism.
Covalent bonds can be classified by the way the electron orbitals overlap, as well as by their displacement towards one of the bonded atoms.
Chemical bonds formed as a result of overlapping electron orbitals along a bond line are called $σ$ -bonds (sigma bonds). The sigma bond is very strong.
$p-$orbitals can overlap in two regions, forming a covalent bond due to lateral overlap:
Chemical bonds formed as a result of “lateral” overlap of electron orbitals outside the communication line, i.e. in two areas are called $π$ -bonds (pi-bonds).
By degree of displacement shared electron pairs to one of the atoms they bond, a covalent bond can be polar And non-polar.
A covalent chemical bond formed between atoms with the same electronegativity is called non-polar. Electron pairs are not shifted to any of the atoms, because atoms have the same EO - the property of attracting valence electrons from other atoms. For example:
those. molecules of simple non-metal substances are formed through covalent non-polar bonds. A covalent chemical bond between atoms of elements whose electronegativity differs is called polar.
Length and energy of covalent bonds.
Characteristic properties of covalent bond- its length and energy. Link length is the distance between the nuclei of atoms. The shorter the length of a chemical bond, the stronger it is. However, a measure of the strength of the connection is binding energy, which is determined by the amount of energy required to break a bond. It is usually measured in kJ/mol. Thus, according to experimental data, the bond lengths of $H_2, Cl_2$ and $N_2$ molecules are respectively $0.074, 0.198$ and $0.109$ nm, and the bond energies are respectively $436, 242$ and $946$ kJ/mol.
Ions. Ionic bond
Let's imagine that two atoms “meet”: an atom of a group I metal and a non-metal atom of group VII. A metal atom has a single electron at its outer energy level, while a non-metal atom just lacks one electron for its outer level to be complete.
The first atom will easily give the second its electron, which is far from the nucleus and weakly bound to it, and the second will provide it with a free place on its outer electronic level.
Then the atom, deprived of one of its negative charges, will become a positively charged particle, and the second will turn into a negatively charged particle due to the resulting electron. Such particles are called ions.
The chemical bond that occurs between ions is called ionic.
Let's consider the formation of this bond using the example of the well-known compound sodium chloride (table salt):
The process of converting atoms into ions is depicted in the diagram:
This transformation of atoms into ions always occurs during the interaction of atoms of typical metals and typical non-metals.
Let's consider the algorithm (sequence) of reasoning when recording the formation of an ionic bond, for example, between calcium and chlorine atoms:
Numbers showing the number of atoms or molecules are called coefficients, and numbers showing the number of atoms or ions in a molecule are called indexes.
Metal connection
Let's get acquainted with how atoms of metal elements interact with each other. Metals usually do not exist as isolated atoms, but in the form of a piece, ingot, or metal product. What holds metal atoms in a single volume?
The atoms of most metals contain a small number of electrons at the outer level - $1, 2, 3$. These electrons are easily stripped off and the atoms become positive ions. The detached electrons move from one ion to another, binding them into a single whole. Connecting with ions, these electrons temporarily form atoms, then break off again and combine with another ion, etc. Consequently, in the volume of the metal, atoms are continuously converted into ions and vice versa.
The bond in metals between ions through shared electrons is called metallic.
The figure schematically shows the structure of a sodium metal fragment.
In this case, a small number of shared electrons bind a large number of ions and atoms.
A metallic bond has some similarities with a covalent bond, since it is based on the sharing of external electrons. However, with a covalent bond, the outer unpaired electrons of only two neighboring atoms are shared, while with a metallic bond, all atoms take part in the sharing of these electrons. That is why crystals with a covalent bond are brittle, but with a metal bond, as a rule, they are ductile, electrically conductive and have a metallic luster.
Metallic bonding is characteristic of both pure metals and mixtures of various metals—alloys in solid and liquid states.
Hydrogen bond
A chemical bond between positively polarized hydrogen atoms of one molecule (or part thereof) and negatively polarized atoms of strongly electronegative elements having lone electron pairs ($F, O, N$ and less commonly $S$ and $Cl$) of another molecule (or its part) is called hydrogen.
The mechanism of hydrogen bond formation is partly electrostatic, partly donor-acceptor in nature.
Examples of intermolecular hydrogen bonding:
In the presence of such a connection, even low-molecular substances can, under normal conditions, be liquids (alcohol, water) or easily liquefied gases (ammonia, hydrogen fluoride).
Substances with hydrogen bonds have molecular crystal lattices.
Substances of molecular and non-molecular structure. Type of crystal lattice. Dependence of the properties of substances on their composition and structure
Molecular and non-molecular structure of substances
It is not individual atoms or molecules that enter into chemical interactions, but substances. Under given conditions, a substance can be in one of three states of aggregation: solid, liquid or gaseous. The properties of a substance also depend on the nature of the chemical bond between the particles that form it - molecules, atoms or ions. Based on the type of bond, substances of molecular and non-molecular structure are distinguished.
Substances made up of molecules are called molecular substances. The bonds between the molecules in such substances are very weak, much weaker than between the atoms inside the molecule, and even at relatively low temperatures they break - the substance turns into a liquid and then into a gas (sublimation of iodine). The melting and boiling points of substances consisting of molecules increase with increasing molecular weight.
Molecular substances include substances with an atomic structure ($C, Si, Li, Na, K, Cu, Fe, W$), among them there are metals and non-metals.
Let's consider the physical properties of alkali metals. The relatively low bond strength between atoms causes low mechanical strength: alkali metals are soft and can be easily cut with a knife.
Large atomic sizes lead to low densities of alkali metals: lithium, sodium and potassium are even lighter than water. In the group of alkali metals, the boiling and melting points decrease with increasing atomic number of the element, because Atom sizes increase and bonds weaken.
To substances non-molecular structures include ionic compounds. Most compounds of metals with nonmetals have this structure: all salts ($NaCl, K_2SO_4$), some hydrides ($LiH$) and oxides ($CaO, MgO, FeO$), bases ($NaOH, KOH$). Ionic (non-molecular) substances have high melting and boiling points.
Crystal lattices
Matter, as is known, can exist in three states of aggregation: gaseous, liquid and solid.
Solids: amorphous and crystalline.
Let us consider how the characteristics of chemical bonds influence the properties of solids. Solids are divided into crystalline And amorphous.
Amorphous substances do not have a clear melting point; when heated, they gradually soften and turn into a fluid state. For example, plasticine and various resins are in an amorphous state.
Crystalline substances are characterized by the correct arrangement of the particles of which they are composed: atoms, molecules and ions - at strictly defined points in space. When these points are connected by straight lines, a spatial framework is formed, called a crystal lattice. The points at which crystal particles are located are called lattice nodes.
Depending on the type of particles located at the nodes of the crystal lattice and the nature of the connection between them, four types of crystal lattices are distinguished: ionic, atomic, molecular And metal.
Ionic crystal lattices.
Ionic are called crystal lattices, in the nodes of which there are ions. They are formed by substances with ionic bonds, which can bind both simple ions $Na^(+), Cl^(-)$, and complex $SO_4^(2−), OH^-$. Consequently, salts and some oxides and hydroxides of metals have ionic crystal lattices. For example, a sodium chloride crystal consists of alternating positive $Na^+$ and negative $Cl^-$ ions, forming a cube-shaped lattice. The bonds between ions in such a crystal are very stable. Therefore, substances with an ionic lattice are characterized by relatively high hardness and strength, they are refractory and non-volatile.
Atomic crystal lattices.
Atomic are called crystal lattices, in the nodes of which there are individual atoms. In such lattices, the atoms are connected to each other by very strong covalent bonds. An example of substances with this type of crystal lattices is diamond, one of the allotropic modifications of carbon.
Most substances with an atomic crystal lattice have very high melting points (for example, for diamond it is above $3500°C), they are strong and hard, and practically insoluble.
Molecular crystal lattices.
Molecular called crystal lattices, in the nodes of which molecules are located. Chemical bonds in these molecules can be both polar ($HCl, H_2O$) and nonpolar ($N_2, O_2$). Despite the fact that the atoms inside the molecules are connected by very strong covalent bonds, weak intermolecular forces of attraction act between the molecules themselves. Therefore, substances with molecular crystal lattices have low hardness, low melting points, and are volatile. Most solid organic compounds have molecular crystal lattices (naphthalene, glucose, sugar).
Metal crystal lattices.
Substances with metallic bonds have metallic crystal lattices. At the sites of such lattices there are atoms and ions (either atoms or ions, into which metal atoms easily transform, giving up their outer electrons “for common use”). This internal structure of metals determines their characteristic physical properties: malleability, ductility, electrical and thermal conductivity, characteristic metallic luster.
A molecule in which the centers of gravity of the positively and negatively charged sections do not coincide is called a dipole. Let us define the concept of “dipole”.
A dipole is a combination of two opposite electric charges of equal magnitude, located at a certain distance from each other.
The hydrogen molecule H2 is not a dipole (Fig. 50 A), and the hydrogen chloride molecule is a dipole (Fig. 50 b). A water molecule is also a dipole. Electron pairs in H 2 O are largely shifted from hydrogen atoms to oxygen atoms.
The center of gravity of the negative charge is located near the oxygen atom, and the center of gravity of the positive charge is located near the hydrogen atoms.
In a crystalline substance, atoms, ions or molecules are in strict order.
The place where such a particle is located is called node of the crystal lattice. The position of atoms, ions or molecules in the nodes of the crystal lattice is shown in Fig. 51.
in g
Rice. 51. Models of crystal lattices (one plane of a bulk crystal is shown): A) covalent or atomic (diamond C, silicon Si, quartz SiO 2); b) ionic (NaCl); V) molecular (ice, I 2); G) metal (Li, Fe). In the metal lattice model, dots represent electrons
Based on the type of chemical bond between particles, crystal lattices are divided into covalent (atomic), ionic and metallic. There is another type of crystal lattice - molecular. In such a lattice, individual molecules are held together by forces of intermolecular attraction.
Ionic crystals(Fig. 51 b) contain positively and negatively charged ions at the sites of the crystal lattice. The crystal lattice is constructed in such a way that the forces of electrostatic attraction of unlike charged ions and the forces of repulsion of like charged ions are balanced. Such crystal lattices are characteristic of compounds such as LiF, NaCl and many others.
Molecular crystals(Fig. 51 V) contain dipole molecules at the crystal nodes, which are held relative to each other by forces of electrostatic attraction, like ions in an ionic crystal lattice. For example, ice is a molecular crystal lattice formed by water dipoles. In Fig. 51 V Symbols for charges are not shown so as not to overload the figure.
metal crystal(Fig. 51 G) contains positively charged ions at the sites of the crystal lattice. Some of the outer electrons move freely between the ions. " Electronic gas"holds positively charged ions in the nodes of the crystal lattice. When struck, the metal does not break like ice, quartz or a salt crystal, but only changes shape. Electrons, due to their mobility, manage to move at the moment of impact and hold the ions in a new position. That is why metals are forged and plastic, bend without destruction.
Rice. 52. Structure of silicon oxide: A) crystalline; b) amorphous. Black dots indicate silicon atoms, light circles indicate oxygen atoms. The crystal plane is shown, so the fourth bond of the silicon atom is not indicated. The dotted line indicates short-range order in the disorder of an amorphous substance
In an amorphous substance, the three-dimensional periodicity of the structure, characteristic of the crystalline state, is disrupted (Fig. 52 b).
Liquids and gases differ from crystalline and amorphous bodies by the random movement of atoms and
molecules. In liquids, attractive forces are able to hold microparticles relative to each other at close distances, comparable to distances in a solid. In gases, there is practically no interaction between atoms and molecules, therefore gases, unlike liquids, occupy the entire volume provided to them. A mole of liquid water at 100 0 C occupies a volume of 18.7 cm 3, and a mole of saturated water vapor occupies 30,000 cm 3 at the same temperature. 
Rice. 53. Various types of interaction of molecules in liquids and gases: A) dipole–dipole; b) dipole–non-dipole; V) non-dipole–non-dipole
Unlike solids, molecules in liquids and gases move freely. As a result of movement, they are oriented in a certain way. For example, in Fig. 53 a, b. it is shown how dipole molecules interact, as well as non-polar molecules with dipole molecules in liquids and gases.
As dipole approaches dipole, the molecules rotate as a result of attraction and repulsion. The positively charged part of one molecule is located near the negatively charged part of the other. This is how dipoles interact in liquid water.
When two non-polar molecules (non-dipoles) approach each other at sufficiently close distances, they also mutually influence each other (Fig. 53 V). Molecules are brought together by negatively charged electron shells surrounding the nuclei. The electron shells are deformed so that a temporary appearance of positive and negative centers occurs in one and the other molecule, and they are mutually attracted to each other. It is enough for the molecules to disperse, and the temporary dipoles again become non-polar molecules.
An example is the interaction between molecules of hydrogen gas. (Fig. 53 V).
3.2. Classification of inorganic substances. Simple and complex substances
At the beginning of the 19th century, the Swedish chemist Berzelius proposed that substances obtained from living organisms be called organic. Substances characteristic of inanimate nature were called inorganic or mineral(derived from minerals).
All solid, liquid and gaseous substances can be divided into simple and complex.
Simple substances are substances consisting of atoms of one chemical element.
For example, hydrogen, bromine and iron at room temperature and atmospheric pressure are simple substances that are in gaseous, liquid and solid states, respectively (Fig. 54 a B C).
Gaseous hydrogen H 2 (g) and liquid bromine Br 2 (l) consist of diatomic molecules. Solid iron Fe(s) exists in the form of a crystal with a metallic crystal lattice.
Simple substances are divided into two groups: nonmetals and metals.
A) b) V)
Rice. 54. Simple substances: A) hydrogen gas. It is lighter than air, so the test tube is capped and turned upside down; b) liquid bromine (usually stored in sealed ampoules); V) iron powder
Nonmetals are simple substances with a covalent (atomic) or molecular crystal lattice in the solid state.
At room temperature, a covalent (atomic) crystal lattice is characteristic of such nonmetals as boron B(s), carbon C(s), silicon Si(s). The molecular crystal lattice has white phosphorus P(s), sulfur S(s), iodine I 2 (s). Some non-metals transform into a liquid or solid state of aggregation only at very low temperatures. Under normal conditions they are gases. Such substances include, for example, hydrogen H 2 (g), nitrogen N 2 (g), oxygen O 2 (g), fluorine F 2 (g), chlorine Cl 2 (g), helium He (g), neon Ne (g), argon Ar(g). At room temperature, molecular bromine Br 2 (l) exists in liquid form.
Metals are simple substances with a metal crystal lattice in the solid state.
These are malleable, plastic substances that have a metallic luster and are capable of conducting heat and electricity.
Approximately 80% of the elements of the Periodic Table form simple substances - metals. At room temperature, metals are solids. For example, Li(t), Fe(t). Only mercury, Hg(l) is a liquid that solidifies at –38.89 0 C.
Complex substances are substances consisting of atoms of different chemical elements
The atoms of elements in a complex substance are connected by constant and well-defined relationships.
For example, water H 2 O is a complex substance. Its molecule contains atoms of two elements. Water always, anywhere on Earth, contains 11.1% hydrogen and 88.9% oxygen by mass.
Depending on the temperature and pressure, water can be in a solid, liquid or gaseous state, which is indicated to the right of the chemical formula of the substance - H 2 O (g), H 2 O (l), H 2 O (t).
In practical activities, as a rule, we deal not with pure substances, but with their mixtures.
A mixture is a combination of chemical compounds of different composition and structure
Let us present simple and complex substances, as well as their mixtures, in the form of a diagram:
Simple
Nonmetals
Emulsions
Reasons
Complex substances in inorganic chemistry are divided into oxides, bases, acids and salts.
Oxides
There are oxides of metals and non-metals. Metal oxides are compounds with ionic bonds. In the solid state they form ionic crystal lattices.
Non-metal oxides– compounds with covalent chemical bonds.
Oxides are complex substances consisting of atoms of two chemical elements, one of which is oxygen, the oxidation state of which is – 2.
Below are the molecular and structural formulas of some non-metal and metal oxides.
Molecular formula Structural formula
CO 2 – carbon monoxide (IV) O = C = O
SO 2 – sulfur oxide (IV)
SO 3 – sulfur oxide (VI)
SiO 2 – silicon oxide (IV)
Na 2 O – sodium oxide
CaO – calcium oxide
K 2 O – potassium oxide, Na 2 O – sodium oxide, Al 2 O 3 – aluminum oxide. Potassium, sodium and aluminum form one oxide each.
If an element has several oxidation states, there are several oxides. In this case, after the name of the oxide, indicate the oxidation state of the element with a Roman numeral in parentheses. For example, FeO is iron (II) oxide, Fe 2 O 3 is iron (III) oxide.
In addition to the names formed according to the rules of international nomenclature, traditional Russian names of oxides are used, for example: CO 2 carbon monoxide (IV) - carbon dioxide, CO carbon monoxide (II) – carbon monoxide, CaO calcium oxide – quicklime, SiO 2 silicon oxide– quartz, silica, sand.
There are three groups of oxides, differing in chemical properties: basic, acidic And amphoteric(ancient Greek: , – both, dual).
Basic oxides formed by elements of the main subgroups of groups I and II of the Periodic Table (oxidation state of elements +1 and +2), as well as elements of secondary subgroups, the oxidation state of which is also +1 or +2. All these elements are metals, so basic oxides are metal oxides, For example:
Li 2 O – lithium oxide
MgO – magnesium oxide
CuO – copper(II) oxide
Basic oxides correspond to bases.
Acidic oxides
formed by non-metals and metals whose oxidation state is greater than +4, for example:
CO 2 – carbon monoxide (IV)
SO 2 – sulfur oxide (IV)
SO 3 – sulfur oxide (VI)
P 2 O 5 – phosphorus oxide (V)
Acidic oxides correspond to acids.
Amphoteric oxides
formed by metals whose oxidation state is +2, +3, sometimes +4, for example:
ZnO – zinc oxide
Al 2 O 3 – aluminum oxide
Amphoteric oxides correspond to amphoteric hydroxides.
In addition, there is a small group of so-called indifferent oxides:
N 2 O – nitric oxide (I)
NO – nitric oxide (II)
CO – carbon monoxide (II)
It should be noted that one of the most important oxides on our planet is hydrogen oxide, known to you as water H2O.
Reasons
In the “Oxides” section it was mentioned that bases correspond to basic oxides:
Sodium oxide Na 2 O - sodium hydroxide NaOH.
Calcium oxide CaO – calcium hydroxide Ca(OH) 2.
Copper oxide CuO – copper hydroxide Cu(OH) 2
Bases are complex substances consisting of a metal atom and one or more hydroxyl groups –OH.
Bases are solids with an ionic crystal lattice.
When dissolved in water, crystals of soluble bases ( alkalis) are destroyed by polar water molecules, and ions are formed:
NaOH(s) Na + (solution) + OH – (solution)
A similar notation for ions: Na + (solution) or OH – (solution) means that the ions are in solution.
The name of the base includes the word hydroxide and the Russian name of the metal in the genitive case. For example, NaOH is sodium hydroxide, Ca(OH) 2 is calcium hydroxide.
If a metal forms several bases, then the oxidation state of the metal is indicated in the name with a Roman numeral in parentheses. For example: Fe(OH) 2 – iron (II) hydroxide, Fe(OH) 3 – iron (III) hydroxide.
In addition, for some grounds there are traditional names:
NaOH – caustic soda, caustic soda
CON – caustic potassium
Ca(OH) 2 – slaked lime, lime water
R
Bases that dissolve in water are called alkalis
They distinguish water-soluble and water-insoluble bases.
These are metal hydroxides of the main subgroups of groups I and II, except for Be and Mg hydroxides.
Amphoteric hydroxides include:
HCl(g) H + (solution) + Cl – (solution)
Acids are complex substances that contain hydrogen atoms that can be replaced or exchanged for metal atoms and acidic residues.
Depending on the presence or absence of oxygen atoms in the molecule, oxygen-free And oxygen-containing acids.
To name oxygen-free acids, the letter - is added to the Russian name of the non-metal. O- and the word hydrogen :
HF – hydrofluoric acid
HCl – hydrochloric acid
HBr – hydrobromic acid
HI – hydroiodic acid
H 2 S – hydrosulphide acid
Traditional names of some acids:
HCl – hydrochloric acid; HF – hydrofluoric acid
To name oxygen-containing acids, the endings - Naya,
-new, if the nonmetal is in the highest oxidation state. The highest oxidation state coincides with the number of the group in which the nonmetal element is located:
H 2 SO 4 – sulfur Naya acid
HNO 3 – nitrogen Naya acid
HClO 4 – chlorine Naya acid
HMnO 4 – manganese new acid
If an element forms acids in two oxidation states, then the ending - is used to name the acid corresponding to the lower oxidation state of the element. true:
H 2 SO 3 – chamois exhausted acid
HNO 2 – nitrogen exhausted acid
Based on the number of hydrogen atoms in a molecule, they are distinguished monobasic(HCl, HNO 3), dibasic(H 2 SO 4), tribasic acids (H 3 PO 4).
Many oxygen-containing acids are formed by the interaction of the corresponding acid oxides with water. The oxide corresponding to a given acid is called its anhydride:
Sulfur dioxide SO 2 - sulfurous acid H 2 SO 3
Sulfuric anhydride SO 3 – sulfuric acid H 2 SO 4
Nitrous anhydride N 2 O 3 – nitrous acid HNO 2
Nitric anhydride N 2 O 5 – nitric acid HNO 3
Phosphoric anhydride P 2 O 5 – phosphoric acid H 3 PO 4
Please note that the oxidation states of the element in the oxide and the corresponding acid are the same.
If an element forms several oxygen-containing acids in the same oxidation state, then the prefix "" is added to the name of the acid with a lower content of oxygen atoms. meta", with a high oxygen content – prefix " ortho". For example:
HPO 3 – metaphosphoric acid
H 3 PO 4 - orthophosphoric acid, which is often called simply phosphoric acid
H 2 SiO 3 – metasilicic acid, usually called silicic acid
H 4 SiO 4 – orthosilicic acid.
Silicic acids are not formed by the interaction of SiO 2 with water; they are obtained in a different way.
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Salts are complex substances consisting of metal atoms and acidic residues.
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NaNO 3 – sodium nitrate
CuSO 4 – copper (II) sulfate
CaCO 3 – calcium carbonate
When dissolved in water, salt crystals are destroyed and ions are formed:
NaNO 3 (t) Na + (solution) + NO 3 – (solution).
Salts can be considered as products of complete or partial replacement of hydrogen atoms in an acid molecule with metal atoms or as products of complete or partial replacement of hydroxyl groups of a base with acidic residues.
When hydrogen atoms are completely replaced, medium salts: Na 2 SO 4, MgCl 2. . Upon partial replacement, they are formed acid salts (hydrosalts) NaHSO 4 and basic salts (hydroxy salts) MgOHCl.
According to the rules of international nomenclature, the names of salts are formed from the name of the acid residue in the nominative case and the Russian name of the metal in the genitive case (Table 12):
NaNO 3 – sodium nitrate
CuSO 4 – copper(II) sulfate
CaCO 3 – calcium carbonate
Ca 3 (PO 4) 2 – calcium orthophosphate
Na 2 SiO 3 – sodium silicate
The name of the acid residue is derived from the root of the Latin name of the acid-forming element (for example, nitrogenium - nitrogen, root nitr-) and the endings:
-at for the highest oxidation state, -it for a lower degree of oxidation of the acid-forming element (Table 12).
Table 12
Names of acids and salts
| Acid name | Acid formula | Name of salts | Examples Soleil |
| Hydrochloric (salt) | HCl | Chlorides | AgCl Silver chloride |
| Hydrogen sulfide | H2S | Sulfides | FeS Sulf eid iron(II) |
| Sulphurous | H2SO3 | Sulfites | Na 2 SO 3 Sulf it sodium |
| Sulfuric | H2SO4 | Sulfates | K 2 SO 4 Sulph at potassium |
| Nitrogenous | HNO2 | Nitrites | LiNO 2 Nitre it lithium |
| Nitrogen | HNO3 | Nitrates | Al(NO 3) 3 Nitre at aluminum |
| Orthophosphoric | H3PO4 | Orthophosphates | Ca 3 (PO 4) 2 Calcium orthophosphate |
| Coal | H2CO3 | Carbonates | Na 2 CO 3 Sodium carbonate |
| Silicon | H2SiO3 | Silicates | Na 2 SiO 3 Sodium silicate |
NaHSO 4 – sodium hydrogen sulfate
NaHS – sodium hydrosulfide
The names of the main salts are formed by adding the prefix " hydroxo": MgOHCl – magnesium hydroxychloride.
Additionally, many salts have traditional names, such as:
Na 2 CO 3 – soda;
NaHCO 3 – baking (drinking) soda;
CaCO 3 – chalk, marble, limestone.
